Process for reducing the sulphur content of gasoline



v. ABELES I 2,378,382

PROCESS FOR REDUCING THE SULPHUR CONTENT OF GASOLINE June 19, 1945.

Filed Feb. 4. 1943 I N VE N TOR. V/c TOR AaELEJ I, II,

-$SEUL m A L unt ATTORNEY.

I Patented June 19, 1945 UNITED STATES PATENT]- OFFICE,

PROCESS FOR REDUCING THE SULPHUR CONTENT OF GASOLINE Victor Abelcs, Nashville, Tenn.

Application February 4, 1943, Serial N0.474,659

4 Claims.

This invention is a new and useful process for reducing the sulphur content of a light hydrocarbon distillate such as naphtha or gasoline produced, for example, by distillation from a crude petroleum. The inventionwill be fully understood from the following description read in corn junction with the drawing which is a diagrammatic plan of apparatus in which the invention maybe carried into efiect'.

Referring to 'the drawin ,,l indicates a pipe still, including inlet 2 communicating with heater coil 3, discharging through outlet l. The coil .3 is housed in a suitable refractory setting -5 heated by burner 6, the products of combustion passing ofl through stack l. i f

Outlet discharges into N which is a rectifying column. This column is provided with a dischargeioutlet I 2 through which bottoms may be withdrawn, with aside outlet i3 through which a cut in vapor phase may be withdrawn; with a side'outlet 14 through which a lower boiling cut in vapor phase may'be withdrawn andwith an outlet, I5 adjacent the upper part of the column inlet 32 through which a gas may be introduced passing upwardly v through foraminous' partition 33 by which it is resolved into fine bubbles which 'commingle with any liquid in the space 34 above the partition. Above the space 34 is a horizontal grate 0r partition 35 upon which is supported 'a solid contact material 36 through which the liquid may pass upwardly passing .outof the'apparatus through side arm' 31. Any excess or unabsorbed gas will escape through upper outlet 38. The liquid from side arm 31 may be returned through valved pipe 39 into the upper-part of'column H ormaybe diverted in whole or in part out of.

the system through valved pipe 'll].

In the operation of the apparatus, a crude petroleum containing light hydrocarbons such as naphtha or gasoline hydrocarbons and higher boiling hydrocarbons is introduced continuously to pipe still I through inlet 2. Such oils normally also contain organicfisulphur bearing compounds, such as, mercaptans, some of which boil within the naphtha or gasolinerange and are therefore responsible at least in part for the sulphur content of any gasoline derived fromsuch crudes.

The crude petroleum so introduced is heated in heater coil 3 to substantial vaporization or to substantially complete vaporization and in this It is preferably equipped with a condensation of the vapors passes off through I outlet I9. I

Outlet I9 communicates with separator 20, the

, function of which is to separate any water present in the condensate. This water passes off from the separator through the bottom outlet 20, while the water. freejcondensate is discharged through is withdrawn through bottom outlet 23. The lighter liquid that has been treated passes off through outlet 24, adjacent the upper part of'the tower. I

The outlet 24 discharges into the intermediate section of the tower 3 I. This tower has a bottom condition is discharged through outlet 4 into the lower part of rectifying column ll within which is maintained a rectifying zone. .Heavy ends or bottoms are taken off continuously through bottom outlet 1 2. A distillate such as gas oil is taken off in vapor phase through side outlet, I3. A lower boiling distillate such as kerosene is taken off in vapor phase through side outlet H. The.

lowest boiling out, i. e., the gasoline or gasoline and naphtha is taken ofi in vapor phase throughupper outlet l5. In heat exchanger I Bthis cut is condensed to liquid phase.' It is then run through the separator diagrammatically .indicated by 20 inwhich it 'isfreed ofany water; The water is withdrawn from the system through the bottom outlet 20, while the water free condensate is discharged through the side outlet 21]" into the lower section of tower 2|. Concentrated caustic solution is introduced through side inlet 22 and after passing downwardly in counter current contact with the ascending gasoline is withdrawn, through bottom outlet 23. The effect of the caustic is to remove sulphur reactive therewith, such as hydrogen sulfide and some mercaptans and the gasoline or mixture of gasoline and naphtha freed of these passes off through the' upper outlet 24.

01 tower 3|. Oxygen which may be in the form of air, but is preferably substantially pure is inpounds react with the mercaptans present, while the oxygen operates to regenerate the metallic compounds simultaneously converting the mercaptans into a form less odorous, negative to the doctor test and therefore less objectionable.

While I prefer this particular, known, sweetening method in association with the other steps that characterize my invention, it will be understood that I am not limited thereto and may in fact employ at this point any of the recognized sweetening reagents. I may, for example, use at this point a sodium plum-bite solution; in this case the amount of added elemental sulphur should not in any event exceed that present in mercaptan form in the gasoline.

On starting up the system the reflux condenser in the upper part of column I l is operated and all of the sweetened gasoline or gasoline and naphtha from outlet 31 is returned through valved pipe 39 into the upper part of column ll. Being in liquid phase it will function as reflux and as it builds up in the system the reflux condenser may be progressively throttled until this gasoline is returning in sufflcient amount to provide all the reflux required in column I I. Thereupon, the valve in pipe 40 is'opened and an amount of gasoline or gasoline and naphtha corresponding to that present in the crude oil coming into the system is withdrawn through pipe 40. The amount of gasoline or gasoline and naphtha continuously recycled through pipe 39 should be at least equal in amount to that contemporaneously withdrawn through pipe 40 and for best results should be at least three times that amount. In a specific case in which it was four times that of the gasoline withdrawn through pipe 40, the amount of sulphur present in the finished gasoline withdrawn from the system was reduced to a minor percentage of that present in the finished gasoline under otherwise identical conditions with the usual once through process.

It will be understood that I may similarly treat any out taken ofi from the rectifying zone even though it is not the cut of lowest boiling point. In this case the sweetened and recycled cut will be re-introduced into the rectifying zone in liquid phase at or below the level at which it was taken off. The cut or cuts of lower boiling point simultaneously taken off from the rectifying zone may, if desired, be simultaneously similarly treated. In any case a cut or bottoms of higher boiling point than that sweetened, in accordance with my process, will be simultaneously taken from the rectifying zone,

The foregoing description is for purposes of illustration and not of limitation and it is therefore my intention that the invention be limited only by the following claims or their equivalents wherein I have endeavored to claim broadly all inherent novelty.

I claim:

1. Process of producing petroleum distillate of reduced sulphur content from a mixture of hydrocarbons containing mercaptans boiling Within the same range which comprises continuously introducing such a mixture into a rectifying zone, taking off from said rectifying zone a petroleum distillate and at least one higher boiling fraction, thereafter treating said distillate in liquid phase with a sweetening agent in amount suflicient to react with the mercaptans contained therein, continuously abstracting from the process an amount of treated distillate corresponding to the distillate contained in the said mixture contemporaneously coming into said rectifying zone and recycling at least a part of the remainder of said distillate into said rectifying zone, the amount of distillateso recycled being at least equal to that abstracted. v

2. Process according to claim 1 in which the sweetening agent includes cupric chloride and free oxygen.

3. Process of producing petroleum distillate of reduced sulphur content 'from a mixture of hydrocarbons containing mercaptans boiling within the same range which comprises continuously introducing such a mixture into a rectifying zone, taking off from said rectifying zone a petroleum distillate and at least one higher boiling fraction, thereafter treating said distillate in liquid phase with a sweetening agent in amount suficient to react with the mercaptans contained therein, continuously abstracting from the process an amount of treated distillate corresponding to the distillate contained in the said mixture contemporaneously coming into said rectifying zone and recycling at least a part of the remainder of said distillate into said rectifying zone the amount of distillate so recycled being at least three times that abstracted.

4:. Process according to claim 3 in which the sweetening agent includes cupric chloride and free oxygen.

VICTOR ABELES. 

